Protective device for use in polyphase-current installations



1,638 Aug. 9, 1927. I R. KELLER ,533

PROTECTIVE DEVICE FOR USE IN POLYPHASE CURRENT INSTALLATIONS Filed Nov.:5. 1925 Patented Aug. 9, 1927.

UNITED STATES PATENT OFFICE.

ROBERT KELLER, OF ENNETBADEN, SWITZERLAND, ASSIGNOR T0 AKTIENGESELL-SCHAIT BROWN BOVERI AND DIE, 0F BAIDEN, SWITZERLAND.

PROTECTIVE DEVICE FOR USE IN POLYPHASE-CUBRENT INSTALLATIONS.

Application filed November 3, 1925, Serial No. 68,617, and in GermanyNovember 17, 1924. i

operation when a certain load has been attained and reducing theexciting current of the generators supplying the installation, so thatthe output is reduced to normal. In polyphase current installationshowever there is a disadvantage in that the effect of the overload onthe regulator varies according to the nature of the overload, i. e.,

whether it occurs on one, two or all the.

phases.

This disadvantage is overcome by the present invention which ensuresthat the regulator shall operate whether the current exceed the limit inone, two or all the phases and whether the currents be leading, laggingor in phase. The object of the invention is attained by providing asmany electrically separate magnetic devices as' there are phases,-- eachof the devices acting independently on the control member of theregulator.

Forms of the invention will now be described with reference to theaccompanying drawings wherein Fig. 1 shows diagrammatically one armbodiment of the invention, and

Fig. 2 shows diagrammatically a second form of the invention.

Figures 3 and 4 illustrate diagrammatically two further embodiments ofthe invention.

In the embodiment of the invention diagrammatically illustrated in Fig.1 a is a resistance inserted in the field circuit of theexciter c of thepolyhasc generator I). This resistance is controlled by a member (5which normally occupies a position in which the resistance a is shortcircuited thereby. The member d is held in the position mentioned by asprin f. The member d carries a plate e w ich' occupies a positionopposite to, but separate from, the armature of an electromagnet g andthe ends of two two-armed levers m, n. The levers m, n 'are connectedwith and operated by the armatures of electromagnets h, i, respectively. k, is, k are tension springs which act of the phases, say,

.on the armatures of the electromagnets R, S, T.

'The operation of the device is as follows If, for example, an overloadoccurs in one in. phase S, the electro-. magnet z' is energized toactuate the lever m which strikes and raises the plate e and with it themember 05. The short circuit on the resistance a is removed, wholly orpartly, the exciting current is reduced and the potential of thegenerator 6 falls. In the case of an overload of equal amount in two orall the phases, the electromagnets energized b the said phases arecaused to 0perate t e member d. In order that the pressure on the platee may be kept practically equal in the case of an overload on one two orall the phases the spring 7'- is ma e as weak as possible in relation tothe pull of the electromagnets g, h, i.

Fig. 2 illustrates diagrammatically another embodiment of the inventionin which the electromagnets g', h, 11, act on Ferraris discs p. Thediscs p are also influenced by springs k which normally hold themagainst a stop g. Now if the current, for example, in phase B exceedsthe predetermined limit, the disc 12 rotates, together with a toothedsegment 0", against the pull of the spring is in the direction indicatedby the arrow. The toothed segment 1- meshes with a toothed wheel aloosely mounted on the shaft 0 of the regulator. When the toothed wheels has rotated through a predetermined angle, a pin t mounted on thetoothed wheel 8 comes in contact with a lever a mounted on the shaft eof the regulator. The shaft of the regulator is connected with a contactsegment at and this contact segment d is operated and is moved in adirection to insert resistance a into the field circuit of the exciterwhen the lever u is acted on by the pin 6.

Referring to Figs. 3 and 4, when an overload occurs on one, two or allof the phases, a SWlLLJAl 1) is operated by the electromagnet orelectromagnets that is or are energized to actuate. The switch 4)controls the circuit of the regulator 10. In the embodiment illustratedin Fig. 3, when an overload occurs on one or more of the phases, thearmature of one or more of the electromagnets. g, h, i strikes theswitch plate f and closes switch '0. The closing of switch '0 places thevibrator coil of the Tyrrill Regulator w in circuit and the fieldcurrent of the exciter is weakened.

In the embodiment illustrated in Fig. 4, the switch a; is opened on anoverloa by at least one of the electromagnets g h, z, and the holding-oncoil 1) of the switc arm az' is de-energized. The switch arm a: isreleased and as it moves resistance a is inserted into the field circuitof theexciter.

The devices shown act equally well on single base circuit as on atwo-phase or a three-p ase circuit.

What I claim is 1. Means for controlling overloads in poly h lnSt8.llB.tl0nS comprising a single regu at member to control the currentsupplied y the generator, a plurality of electrically separateelectromagnetic devices connected one in each phase and an operativeconnection between each electromagnetic device and the regulatingmember.

2. Means for controlling overloads in poly hase installations comprisinga single regu ating member to control the current supplied thegenerator, a plurality of electrically separate electromagnetic devices,a plurality of current transformers -connected one infeach phase witheach secondary connected to a separate electromagnetic device, and anoperative connection between each electromagnetic device and theregulating member.

3. Means for controlling overloads in poly hase installations comprisinga single regu ating member to control the current.

supplied by the generator, a plurality of electricallyse arateelectromagnetic devices one connecte in each phase and each controlledby a-separate spring and an operative connection between eachelectromagnetic device and,the regulating member.

4. Means for controlling overloads in poly hase installations comprisinga single regu atin member to control the current supplied y thegenerator, a plurality of electrically separate electromagnetic deviceseach controlled by a separate spring, a plurality of currenttransformers connected one in each phase with each secondar connected toa separate electromagnetic. evice and an operative connection betweeneach electromagnetic device 'and the regulating member.

5. Means for controlling overloads in polyphase installations comprisinga single regu atin member to control the current supplied y thegenerator, a plural1ty of electrically separate electromagnetic devicesconnected one in each phase, and an opera tive connection between eachelectromagnetic device and the regulating member having a time lagbetween the commencement of operation of the electromagnetic device andits action on the regulating member.

6. Means for controlling overloads in polyphase installations comprisinga single regu ating member to control the current supplied by thegenerator, a plurality of electrically separate electromagnetic devices,a plurality of current transformers connected one in each phase witheach sec-.

to vary the amount of said resistance con- I nected in the circuit, aplurality of electrically separate electromagnetic devices connected onein each phase of the polyphase installation, and an operative connectionbetween each electromagnetic device and the means to vary the amount ofthe resistance connected in the circuit.

8. Means for controlling overloads iii polyphase installationscomprising a resistance connected in the field circuit of the exciter ofthe polyphase generator, means to vary the amount of said resistanceconnected in the circuit, a plurality of electricall separateelectromagnetic vdevices, a plura ity of current transformers connectedone in each phase with each secondar connected to a separateelectromagnetic evice and an operative connection between eachelectromagnetic device and the means to vary the amount of theresistance connected in the circuit.

9. Means for controlling overloads in polyphase installations com risinga resistance connected in the field circuit of the exciter of thepolyphase nerator, means to vary the amount of saitf resistanceconnected in the circuit, a plurality of electrically separateelectromagnetic devices connected one in each phase of the polyphaseinstallation, and an operative connection between each electromagneticdevice and the means to vary the amount of the resistance having a timelag between the commencement of operation of the electrmagnetic deviceand its action on the means to vary the amount of the resistance.

10. Means for controlling overloads in polyphase installationscomprising a resistance connected in the field circuit of the exciter ofthe polyphase generator, means to var the amount of said resistanceconnected in the circuit, a plurality of electrically separateelectromagnetic devices, a plurality of current transformers connected,one in each phase with each secondar connected to a separateelectromagnetic evice, and an operative connection between each electromagnetic device and the means to vary the amount of the resistancehavin a time lag between the commencement 0 operation of theelectromagnetic device and its action on the means to vary the amount ofthe resistance.

11. The combination with a polyphase penerator having a field wind' of areguator for controlling the current m said field

